NEW YORK -- Pope Benedict XVI received an ecstatic welcome from 57,000 faithful in Yankee Stadium for the final Mass of his six-day visit to the U.S., drawing applause when he spoke of protecting unborn children and when he called a new generation to priesthood and religious life.

During this election year visit he has avoided politically explosive issues, putting most of his emphasis on world peace, aid for the poor and care for the environment. But, while calling young people to put their faith in Christ into action, he made his strongest statement of the visit regarding abortion.

He asked them to uphold "truths which alone can guarantee respect for the inalienable dignity and rights of each man, woman and child in our world -- including the most defenseless of all human beings, the unborn child in the mother's womb," he said, to long, loud applause.

He urged Catholics to continue to apply their faith by working for the common good.

"Praying fervently for the coming of the kingdom also means being constantly alert for the signs of its presence and working for its growth in every sector of society," the pope said. "It also means rejecting a false dichotomy between faith and political life."

The crowd had waited hours to see him, while serenaded by performers including Harry Connick Jr. and the Harlem Gospel Choir. Enormous silk doves on high poles, looking like a great flock of birds circling the stadium, floated above the popemobile as it entered the stadium. As the pope appeared, the crowd burst into cheers, chanting his name and shouting "Viva il Papa," Italian for "Long live the pope."

Pope Benedict was the third pope to celebrate Mass in Yankee Stadium, after Pope Paul VI in 1965 and Pope John Paul II in 1979. Though that makes it the site of more papal visits than any other U.S. venue, the stadium will be torn down when the new ballpark rising next to it is completed. The altar was at second base, with an enormous papal coat of arms covering the pitchers mound.

The 81-year-old pope still seemed moved by his experience with 25,000 teens and young adults at a youth rally the day before. Those young people "are the church's future, and they deserve all the prayer and support that you can give them," he said.

In his parting words, which he said were aimed at young people, he said, "May you step forward and take up the responsibility which your faith in Christ sets before you. Let your faith and love bear rich fruit in outreach to the poor, the needy and those without a voice."

Finally, he called for more youth to become priests, deacons, sisters and brothers.

"Young men and women of America, I urge you: Open your hearts to the Lord's call to follow him in the priesthood and the religious life. Can there be any greater mark of love than this: to follow in the footsteps of Christ, who was willing to lay down his life for his friends?" he asked, drawing applause once again. When he summarized his homily briefly in Spanish, the same request also received applause.

Tom Quirin, 19, who attended with a small group of fellow students from St. Vincent College in Latrobe, called being in the pope's presence, "incredible."

"I've never been around so many believers at one time," said the freshman from Greenfield.

Melissa Evans, 21, a junior from Apollo, was struck by how engaged the pope appeared to be. "He smiled the entire time. The crowd was really into it. Every time they started cheering for him he would raise his hands in appreciation," she said.

Ben Probst, 21, a sophomore from West Deer, said he was "in ecstasy" after the Mass. Seeing the pope deepened his faith, he said, "because he represents everything that you believe in. I don't think it will change my involvement in the church from what it already is, but it is a memory that I will always be able to look back to."

The Rev. Frank Almade, pastor of the Catholic Community of Sharpsburg, was among hundreds of priests to distribute Communion. He was thrilled with the third row seat he had near the visitors' dug-out, and with the opportunity to gather around the altar as the pope consecrated the bread and wine. He felt overwhelmed, both by the presence of the pope and the response of the people, he said.

"Sometimes as a priest I wonder what good I do. His presence here was inspiring," he said. "It gave me a renewed appreciation that I can't take the presence of myself or any other person for granted."

Bishop David Zubik of Pittsburgh, who had had an opportunity to hear Pope Benedict in person several times this week, noted a renewed enthusiasm in the elderly pope's voice, which he believed was a response to the obvious love and support of the people in Yankee Stadium.

"There was a lot of electricity amongst the people here," he said. The applause for the pope's statements about vocations and the call to priesthood "are a pretty good barometer of where our people are. And that's great."

Chip Kelsch, 53, a staff assistant at St. Paul Seminary in East Carnegie, was among about 100 Pittsburgh diocesan employees and volunteers to attend the Mass. He was moved to be in the pope's presence, he said, but it also drove home the point that Jesus is present in the Mass no matter who celebrates it.

"When your parish priest says Mass and Bishop Zubik says Mass and the pope says Mass, it's the same Mass," he said.

Earlier, on a chilly, gray morning, the pope blessed the site of the Sept. 11, 2001 terror attacks and pleaded with God to bring "peace to our violent world," The Associated Press reported.

The visit by Benedict to ground zero was a poignant moment in a trip marked by unexpectedly festive crowds such as the one at Sunday's Mass.

Benedict was driven in the popemobile part-way down a ramp now used mostly by construction trucks to a spot by the north tower's footprint. He walked the final steps, knelt in silent prayer, then rose to light a memorial candle.

Addressing a group that included survivors, clergy and public officials, he acknowledged the many faiths of the victims at the "scene of incredible violence and pain."

The pope also prayed for "those who suffered death, injury and loss" in the attacks at the Pentagon and in the crash of United Airlines Flight 93 in Shanksville, Somerset County. More than 2,900 people were killed in the four crashes of the airliners hijacked by al-Qaida.

"God of peace, bring your peace to our violent world," the pope prayed. "Turn to your way of love those whose hearts and minds are consumed with hatred."

Benedict invited 24 people with ties to ground zero to join him: survivors, relatives of victims and four rescue workers. He greeted each member of the group individually as a string quartet played in the background. In his prayer, he also remembered those who, "because of their presence here that day, suffer from injuries and illness."

New York deputy fire chief James Riches, father of a fallen Sept. 11 firefighter, said the pope's visit gave him consolation.

"We said 'Where was God?' on 9/11, but he's come back here today and they've restored our faith," Chief Riches said.

The site where the World Trade Center was destroyed is normally filled with hundreds of workers building a 102-story skyscraper, a memorial and transit hub. It bears little resemblance to the debris-filled pit where crews toiled to remove twisted steel and victims' remains.

The remains of more than 1,100 people have never been identified.

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